Guys, my car has problem holding constant speed if the rpms are below 3900. I've got a 90 STD hatch with a 1st gen b16a.

Here are some of the things I've tried:
(1a) search function on HT

then on the car
(1) adjust TPS to .45 volt at idle,
(2) check harness for shorted connections
(3) check the intake manifold and throttle body for vaccuum leaks
(4) check ignition timing, set at stock.
(5) new dizzy rotor and cap from acura dealer
(6) check all vacuum connections for leaks


Any help would be appreciated: